The Simultaneous Photooxidation of As(III) and Photoreduction of Cr(VI) in the Presence of Fe(III) in Aqueous Solution by UV/TiO2 Process: Performance and Mechanism

Photocatalytic redox removal of As(III) and Cr(VI) in aqueous solution was investigated by UV/TiO2/Fe(III) process under various conditions. Fabricated TiO2 film was synthesized by the impregnation method, and used as photocatalyst in this study. The simultaneous removal of As(III) and Cr(VI) enhanced by 55% and 24% by adding Fe(III) in acidic solution under UV irradiation within 90 min. The reaction rate for As(III) oxidation and Cr(VI) reduction reached the highest value in acidic solution and high UV light intensity. The effect of inorganic ions on As(III) removal efficiency followed the order of SO42- > Cl > NO (-)(3)(,) meanwhile, there was no inhibition on Cr(VI) reduction. Trapping experiment results indicated that the photogenerated holes coupled with *OH radicals contributed to As(III) oxidation; photogenerated electrons and Fe(II) were responsible for Cr(VI) reduction. Kinetic analysis using Langmuir-Hinshelwood (L-H) model for As(III) photooxidation and Cr(VI) photoreduction were presented and the possible mechanism was proposed in this study.